Cheick Modibo Diarra, Microsoft Corp's chairman for Africa, has been appointed Mali's interim prime minister, tasked with helping to restore civilian rule to the West African country after last month's coup.

The appointment of Diarra, a former NASA astrophysicist, was announced on Tuesday in a statement read out on state television.

Earlier on Tuesday, soldiers arrested the head of one of Mali's biggest political parties, Soumaila Cisse, hours after a former prime minister was detained by military personnel, officials said. The arrests raised fresh questions about whether the military was still in control of the nation despite a handover of power to a civilian leader.

The coup leaders who ousted Mali's democratically elected president last month recently handed over power to an interim civilian leader, Dioncounda Traore, but the military rulers' leader has also said he will play an important role in Mali's political future.

The European Union delegation in Mali issued a statement expressing concern about the arrests, calling for "an urgent clarification and their immediate release".

The West African regional bloc ECOWAS, the EU and the United States all want to see the military rulers back in their barracks and out of politics as soon as possible.

The latest arrests suggest that the military rulers have yet to accept this.

Arrests

Cisse was arrested in front of his home in Bamako, according to Abdoul Malick Diallo, a member of parliament from Cisse's party.

Diallo said that Cisse was hurt during the arrest but that he could not say how serious the injury was.

Cisse was one the front-runners for the presidential election that was due to take place on April 29.

Modibo Sidibe, a former Malian prime minister, was re-arrested by military personnel just days after being released from custody.

Sidibe was among around a dozen politicians who were arrested immediately after the military coup and who were released following the handover to the civilian interim leader.

Amid the political upheaval, separatist rebels in northern Mali have declared an independent state that is larger than France.

The power vacuum also has allowed an Islamic faction that wants to impose Shariah law in the area to flourish.